This invention relates to embodiments of displacement sensing devices utilizing adjustable tuned circuitry. In the prior art, the use of tuned circuits is well known, however, applicant is aware of no prior art which utilizes the concept of the tuned circuit in the manner with which tuned circuits are used in the present invention. The following prior art is known to applicant:
U.S. Pat. No. 2,495,157 to Browne, Jr. discloses an electro-magnetic device including an armature having lateral projections which extend adjacent a core having primary and secondary windings. A voltage is connected to the primary winding and the voltage induced in the secondary winding is dependent upon the position of the armature with respect to the secondary winding. An indicator is provided to indicate the induced voltage. This invention is vastly different from the inventions disclosed herein mainly because (1) the source and the sensor are connected to the same core and as such are not separated as is the case in the present invention, (2) there is no use in this patent of a passive resonant circuit as is used in the present invention, (3) there is no use of frequency sweeping to detect the resonance, and (4) the patent only discloses the measurement of the displacement of one magnetic core whereas the systems of the present invention may measure the displacement of several ferrite rods in their respective resonant circuits simultaneously. A further distinction lies in the fact that -he indication means of the present invention comprises a computerized readout whereas in the patented invention a simple indicator is used.
U.S. Pat. No. 3,420,222 to Noe, et al. discloses a device designed to detect physiological movement. As shown in FIG. 1, a primary coil hasa voltage induced therein by an oscillator (FIG. 3). Any movement of the core located within the coil caused by movements of the legs connected to the core induces voltages in the coils indicative of the position of the core. This device is different from the inventions disclosed herein for the same reasons noted above with respect to U.S. Pat. No. 2,495,157. It is further noted that Noe, et al comprises a balanced bridge type arrangement which is different from the teachings of the present invention.
U.S. Pat. No. 3,735,244 to Gamtau, et al. discloses a device wherein a coil forms a part of a tuned circuit with a core extending through the coil. An oscillator is utilized to provide voltage to the coil and as the position of the core within the coil changes, the amplitude of the oscillations change as an indication thereof. The teachings of this patent are significantly different from the teachings of the present invention in that (1) the source and the sensor are not separated as is the case in the present invention, (2) no passive resonant circuit is used, (3) no frequency sweep is used, (4) the patented system is only usable to measure the displacement of one magnetic core whereas the systems of the present invention may measure the displacement of several ferrite rods in their respective passive resonant circuits simultaneously, and (5) the computerized readout and calculation aspect of the present invention are not taught or suggested in this patent.
U.S. Pat. No. 4,075,553 to Bouverot, et al. discloses a device which utilizes the concept of "phase change" to determine the presence of a metallic object. The device includes a transmitter coil and receiver coils. When a metallic object is present, a phase difference occurs which is sensed to the use of a phase comparer. This patent is believed to be only generally related to the inventions disclosed herein since the invention disclosed therein measures only the presence of a metallic object and not its exact position. Other differences like those described hereinabove are also present between the teachings of this patent and those of the present invention.
U.S. Pat. No. 4,112,365 to Larson, et al. is believed to be similar to the above discussed U.S. Pat. No. 4,075,553 to Bouverot, et al. with the further provision of utilizing phase shift to determine the position and/or velocity of an object. The effective impedance of a sensing coil changes due to the movement of metallic material, which causes the phase of voltage over the coil to shift. This phase is indicative of the position of the object and the rate of the phase shift is indicative of the speed of the object. Significantly, in this patent, the source and the sensor are not separated which is vastly different from the teachings of the present invention wherein the source and sensor comprise individual components separated from one another by significant distances.
U.S. Pat. No. 4,134,065 to Bauer, et al. discloses a system wherein the position of a core with respect to a coil system is indicated by the phase shift in an oscillating voltage. In this invention, the phase shift is determined and thereby the core position is calculated. This patent is believed to be similar to U.S. Pat. No. 2,495,157 in that the displacement of a magnetic core is directly converted into phase information. As such, the differences between this patent and the present invention are similar to the differences between U.S. Pat. No. 2,495,157 and the present invention.
U.S. Pat. No. 4,263,551 to Gregory, et al. discloses a system wherein the presence of a metallic object between two coils is detected through a detector sensitive to phase change. This invention is believed to be different from the present invention in that (1) the source and the sensor are not separated, (2) the source and the sensor are wound around the same magnetic core, (3) only the presence of the conductive object is measured and not the exact position thereof, and (4) no passive resonant circuit or frequency sweep are used.
U.S. Pat. No. 4,350,954 to Seilly discloses an inductive type displacement transducer which includes a core within windings with the inductance thereof being dependent upon the extent to which the core is within the windings. This system is similar to that which is disclosed in U.S. Pat. No. 3,735,244 differing mainly therefrom in that the sensor coil is wound somewhat differently and a reference coil is used. The teachings of this patent differ from the teachings of the present invention for the same reasons discussed hereinabove with respect to U.S. Pat. No. 3,735,244.
U.S. Pat. No. 3,891,918 to Ellis discloses a linear displacement transducer utilizing an oscillator wherein the oscillator includes a coil with a moveable magnetic core as a part thereof. The movement of the magnetic core changes the inductance of the coil and thereby the frequency of the oscillator. The frequency of the oscillator is measured and is indicative of the displacement of the magnetic core with respect to the coil. Again, this patent differs from the teachings of the present invention for the same reasons discussed hereinabove with respect to U.S. Pat. No. 3,735,244. Mainly, it is noted that in Ellis, the source and the sensor are interconnected, no passive resonant circuit is used, there is no use of frequency sweep to determine positioning and there is no computerized calculation and readout in this system.
The following patents are also known to applicant but are believed to be only generally related to the teachings of the present invention: U.S. Pat. Nos. 2,630,559, 2,949,910, 3,020,527, 3,043,309, 3,253,588, 3,777,255, 3,782,188, 3,911,899, 3,990,065, 4,026,276, 4,107,604, 4,206,769, 4,207,520, 4,229,696, 4,168,496, 4,252,129, 4,277,828.